Polymer brushes have become a significant focus of polymer research with the need for straightforward and versatile surface modification. With the development of controlled radical polymerization from surfaces, new theoretical models, and sophisticated characterization tools, the resulting ability to control brush density and brush thickness gives unparalleled control over surface properties and functionality. By increasing brush density, a stretched brush conformation is formed as a result of constraining the cross-sectional area of that brush strand which thereby influences the interactions of molecules with the brush surface. The associated residual stress also gives polymer brushes properties distinct from an equivalent layer of coated polymer chains. Examples of uncharged and charged “grown from” polymer brushes, the effect of architecture on physical behavior, and the influence of nanoscale patterning will be described. The use of brush surfaces in biology relevant applications will be discussed and...

50th Anniversary Perspective: Polymer Brushes: Novel Surfaces for Future Materials

While the world faces an increased scarcity in fresh water supply, it is of great importance that water from industry and waste streams can be treated for re-use. One of the largest waste streams in the oil and gas industry is produced water. After the phase separation of oil and gas, the produced water is left. This mixture contains dissolved and dispersed hydrocarbons, surfactants, clay particles and salts. Before this water can be used for re-injection, irrigation or as industrial water, it has to be treated. Conventional filtration techniques such as multi media filters and cartridge filters, are able to remove the majority of the contaminants, but the smallest, stabilized oil droplets (<10 μm) remain present in the treated water. In recent years, research has focused on membranes to remove these small oil droplets, because this technology requires no frequent replacement of filters and the water quality after treatment is better. Membranes however suffer from fouling by the contaminants in produced water, leading to a lower clean water flux and increased energy costs. Current research on produced water treatment by membranes is mainly focused on improving existing processes and developing fouling-resistant membranes. Multiple investigations have determined the importance of different factors (such as emulsion properties and operating conditions) on the fouling process, but understanding the background of fouling is largely absent. In this review, we describe the interaction between the membrane and a produced water emulsion from a colloidal perspective, with the aim to create a clear framework that can lead to much more detailed understanding of membrane fouling in produced water treatment. Better understanding of the complex interactions at the produced water/membrane interface is essential to achieve more efficient applications.

Produced water treatment by membranes: A review from a colloidal perspective.

We experimentally investigate drop impact dynamics onto different superhydrophobic surfaces, consisting of regular polymeric micropatterns and rough carbon nanofibers, with similar static contact angles. The main control parameters are the Weber number We and the roughness of the surface. At small We, i.e., small impact velocity, the impact evolutions are similar for both types of substrates, exhibiting Fakir state, complete bouncing, partial rebouncing, trapping of an air bubble, jetting, and sticky vibrating water balls. At large We, splashing impacts emerge forming several satellite droplets, which are more pronounced for the multiscale rough carbon nanofiber jungles. The results imply that the multiscale surface roughness at nanoscale plays a minor role in the impact events for small We less than or approximately equal 120 but an important one for large We greater than or approximately equal 120. Finally, we find the effect of ambient air pressure to be negligible in the explored parameter regime We less than or approximately equal 150.

Drop Impact upon Micro- and Nanostructured Superhydrophobic Surfaces

Room-temperature gas sensors have aroused great attention in current gas sensor technology because of deemed demand of cheap, low power consumption and portable sensors for rapidly growing Internet of things applications. As an important approach, light illumination has been exploited for room-temperature operation with improving gas sensor’s attributes including sensitivity, speed and selectivity. This review provides an overview of the utilization of photoactivated nanomaterials in gas sensing field. First, recent advances in gas sensing of some exciting different nanostructures and hybrids of metal oxide semiconductors under light illumination are highlighted. Later, excellent gas sensing performance of emerging two-dimensional materials-based sensors under light illumination is discussed in details with proposed gas sensing mechanism. Originated impressive features from the interaction of photons with sensing materials are elucidated in the context of modulating sensing characteristics. Finally, the review concludes with key and constructive insights into current and future perspectives in the light-activated nanomaterials for optoelectronic gas sensor applications.
Highlights:
1 Operations of metal oxide semiconductors gas sensors at room temperature under photoactivation are discussed.2 Emerging two-dimensional (2D) materials-based gas sensors under light illumination are summarized.3 The advantages and limitations of metal oxides and 2D-materials-based sensors in gas sensing at room temperature under photoactivation are highlighted.

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Room-Temperature Gas Sensors Under Photoactivation: From Metal Oxides to 2D Materials

Influence of surfactant and electrolyte concentrations on surfactant Adsorption and foaming characteristics

Polyelectrolyte (PE) brushes are a special class of polymer brushes (PBs) containing charges. Polymer chains attain “brush”-like configuration when they are grafted or get localized at an interface (solid–fluid or liquid–fluid) with sufficiently close proximity between two-adjacent grafted polymer chains – such a proximity triggers a particular nature of interaction between the adjacent polymer molecules forcing them to stretch orthogonally to the grafting interface, instead of random-coil arrangement. In this review, we discuss the theory, synthesis, and applications of PE brushes. The theoretical discussion starts with the standard scaling concepts for polymer and PE brushes; following that, we shed light on the state of the art in continuum modelling approaches for polymer and PE brushes directed towards analysis beyond the scaling calculations. A special emphasis is laid in pinpointing the cases for which the PE electrostatic effects can be de-coupled from the PE entropic and excluded volume effects; such de-coupling is necessary to appropriately probe the complicated electrostatic effects arising from pH-dependent charging of the PE brushes and the use of these effects for driving liquid and ion transport at the interfaces covered with PE brushes. We also discuss the atomistic simulation approaches for polymer and PE brushes. Next we provide a detailed review of the existing approaches for the synthesis of polymer and PE brushes on interfaces, nanoparticles, and nanochannels, including mixed brushes and patterned brushes. Finally, we discuss some of the possible applications and future developments of polymer and PE brushes grafted on a variety of interfaces.

Polyelectrolyte brushes: theory, modelling, synthesis and applications

Colloidal Transfer Printing–Mediated Fabrication of Zinc Oxide Nanorods for Self‐Cleaning Applications

Inspired by the self-cleaning ability of lotus leaves and stickiness (towards water) of rose petals, we investigate the droplet impact dynamics on such bioinspired substrates. Impact studies are ca...

https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2019.0260

Dynamics of droplet impingement on bioinspired surface: insights into spreading, anomalous stickiness and break-up

An ordered array of 1D ZnO nanorods obtained by colloidal templating is shown to dramatically enhance the sensing response of NO x at room temperature by confining light and creating periodic structures. The sensitivity is measured for a concentration varying from 2 to 10 ppm (response 53% at 10 ppm) at room temperature under white light illumination with ≈225 nm hole diameter. In contrast, structures with ≈450 nm hole size show better sensing under (response 98% at 10 ppm) elevated temperatures in dark conditions, which is attributed to the increased surface chemical interactions with NO x molecules due to the porous nature and enhanced accessible surface area of ZnO nanorods. Further, the decoration of ZnO Nanorods with gold nanoparticles shows enhanced sensor performance (response 130% at 10 ppm) due to localized surface plasmon resonance under white light illumination. The findings may lead to new opportunities in the visible light-activated room-temperature NO x sensors for healthcare applications.

Light Trapping-Mediated Room-Temperature Gas Sensing by Ordered ZnO Nano Structures Decorated with Plasmonic Au Nanoparticles.

Spin coating is a simple and rapid method for fabricating ordered monolayer colloidal crystals on flat as well as patterned substrates. In this article, we show how a combination of factors, partic...

https://pubs.acs.org/doi/pdf/10.1021/acsomega.8b02002

Meneka Banik

Papers

Polyelectrolyte brushes: theory, modelling, synthesis and applications

Colloidal Transfer Printing–Mediated Fabrication of Zinc Oxide Nanorods for Self‐Cleaning Applications

Dynamics of droplet impingement on bioinspired surface: insights into spreading, anomalous stickiness and break-up

Light Trapping-Mediated Room-Temperature Gas Sensing by Ordered ZnO Nano Structures Decorated with Plasmonic Au Nanoparticles.

Fabrication of Ordered 2D Colloidal Crystals on Flat and Patterned Substrates by Spin Coating.